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Full text of "Maintenance and Repair"

Sunbeam Food Processor Triac Replacement 



MakejProjects 



Sunbeam Food Processor Triac 
Replacement 

Written By: Erich H 



SUMMARY 

A common fault in motorized kitchen appliances is failure of the speed control Triac and/or 
associated Diac. This teardown shows you how to get to and replace the Triac and Diac in a 
Sunbeam food processor. 



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Sunbeam Food Processor Triac Replacement 



Step 1 — Sunbeam Food Processor Triac Replacement 







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• The Sunbeam food processor. 
When plugged into the wall it starts 
at full speed, and the speed control 
dial can't turn it off or adjust the 
speed. 

• This is a common mode of failure 
when a speed control Triac has 
gone short circuit, or failed 
partially, becoming easily triggered. 
This usually happens after a 
voltage spike from an inductive 
load, like the motor in the 
appliance, or something else 
plugged in nearby. 

• Do not under any circumstances 
dismantle the unit with power 
applied, as it is double insulated 
and you could be electrocuted and 
a residual current earth leakage 
device will probably not be able to 
trip to save you. 

• If you are not confident with mains 
wiring, get someone who is to do 
this repair for you. 



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Sunbeam Food Processor Triac Replacement 



Step 2 




• The utensil drawer is removed by tilting it out and pulling it out. 

• This exposes two screws which need to be undone. 

Step 3 




• With the 2 screws removed from the utensil alcove, the lid of the unit can be carefully 
popped off revealing the safety interlock mechanism and another screw. 

• Carefully pry the toggle off of the plastic split pin, and remove it from the associated 
linkages. 

• Remove the screw. 



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Sunbeam Food Processor Triac Replacement 



Step 4 




• Next, the speed control dial must be carefully popped out. 

• This exposes the rotary switch underneath. 



Step 5 




• Next, the transmission spindle must be freed. Identify the plastic locking insert on the 
spindle and carefully pop it out. 

• This allows the plastic spindle to be lifted off of the metal drive shaft, which will allow the 
entire housing to be removed. 

• Undo all of the screws on the underside of the food processor, including the recessed one 
in the middle. You should now be able to lift the entire upper housing off of the base and 
internals. 

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Sunbeam Food Processor Triac Replacement 



Step 6 




• The drive mechanism can be inspected by lifting it up off the base plate. 

• The base plate is shown. 

Step 7 





• The motor housing can be inspected, and the first photo shows the armature and carbon 
brushes of the motor. 

• The second photo shows the safety interlock switches, which are actuated via the toggle 
you removed earlier, when the mixing bowl is locked into place. 

• The remaining third side of the motor housing has the switchboard/PCB subassembly 
attached, with the "pulse" microswitch and rotatory on/off and speed control switch 
exposed 



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Sunbeam Food Processor Triac Replacement 



Step 8 




• These photographs show the switchboard and speed control PCB still attached to the 
motor housing in more detail, and the wires passing between them. 

• The second photograph shows the active and neutral coming into the speed control PCB, 
and the active and neutral going off to the motor. 

• If your motor is on all the time, the problem is likely to be the PCB sitting between the 
power coming into the PCB, and the power going out from the PCB to the motor, i.e. the 
PCB is the problem. 



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Sunbeam Food Processor Triac Replacement 



Step 9 




• The switchboard/PCB subassembly can be removed from the motor housing by undoing 
two screws. The switchboard can be removed from the PCB with removal of another two 
screws. 

• The second photo shows the PCB pads that interest us outlined in red. They are the PCB 
pads for the TO-220 BT137 600V Triac, and the two pads for the DB3 Diac. 

• The third photo shows the TO-220 Triac (black with three legs), and the DB3 diac to its 
right (small blue cylinder with the PCB "Diac" label above it). 

• Replace the DB3 Diac and the BT137 Triac with new ones (costing a few dollars at most) 
after desoldering the old ones from the PCB. 

• Reassemble the unit completely, following the steps in reverse, and apply power only once 
it is safe to do so. 



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